Generally an optical scanner heretofore employs a spectral apparatus to spectralize an optical signal by the principle of optical projection, however, the conventional spectral apparatus has some disadvantages as below:
1. Please refer to FIG. 1, which is a filter bracket 5 having red 1, green 2, blue 3, and transparent 4 filters to be attached on a plane thereof. Said filter bracket 5 is provided between an object to be scanned and a set of lens for moving reciprocally by means of a driving mechanism 6, such that a light signal can pass different filters to achieve a spectral effect of said light signal. The disadvantage is that there will exists an inertia when said filter bracket 5 is moving, so a vibration will be generated to influence the stability of the spectral apparatus. In addition, the lateral movement of the filter bracket 5 will occupy a larger space within the scanner and should be improved.
2. Please refer to FIG. 2, which is a rotary drum type spectral apparatus 1 provided between an object 2 and a set of lens 3 for rotating by means of a motor 4 to spectralize an optical signal by filters of different colors on said rotary drum type spectral apparatus, wherein FIG. 2(a) is a top view of said spectral apparatus 1, and FIG. 2(b) is a side view of said spectral apparatus 1. However, since said rotary drum type spectral apparatus 1 is positioned in an optical path formed by reflective mirrors M1, M2, M3 and lens 3, which results in a big volume and a higher cost, and causes vibration during rotating.